#include<stdio.h>
int main() {
	char good_people;
	for (good_people = 'A'; good_people <= 'D'; good_people++) 
		if (((good_people != 'A')+ (good_people == 'C')+ (good_people == 'D') + (good_people != 'D'))== 3)
			printf("%c\n", good_people);
	return 0;
}




